fixup! lib/zodb: Add tests for critical ZODB properties that Wendelin.core 2 will depend on

lib/tests/testprog/zloadrace.py:90:1 'ZODB.FileStorage.FileStorage' imported but unused

This amends commit c37a989d.

lib/tests/testprog/zloadrace.py

@@ -87,7 +87,6 @@ concurrency bugs that lead to corrupt data.
 
 from __future__ import print_function
 from ZODB import DB
-from ZODB.FileStorage import FileStorage
 from ZODB.POSException import ConflictError
 import transaction
 from persistent import Persistent